An automotive vehicle is provided with an air conditioning system for controlling the temperature of a room air of the vehicle. As shown in FIG. 1, a conventional air conditioning system includes an air conditioning case 10 in which a blower 20 is installed. The blower 20 includes a blower fan 22 and a blower motor 24 for driving the blower fan 22. The blower 20 serves to inhale an external air or an internal air through an external air inlet port 12 or an internal air inlet port 14 of the air conditioning case 10 and then to feed the inhaled air to an internal passageway 16 of the air conditioning case 10.
The air conditioning system further includes an evaporator 30 arranged inside the internal passageway 16 of the air conditioning case 10. The evaporator 30 includes a coolant tube (not shown) through which coolant can flow. The evaporator 30 serves to cool the air passing through the internal passageway 16 and also to introduce the cooled air into a vehicle room, thereby keeping the vehicle room at a pleasant temperature.
The air conditioning system further includes an ionizer 40 for emitting positive ions and negative ions toward the air flowing through the internal passageway 16. As illustrated in FIGS. 1 and 2, the ionizer 40 is installed on the upstream side of the evaporator 30 and includes a main body 42 attached to a side wall of the air conditioning case 10, first and second protection pipes 44 and 45 extending from the main body 42 toward the internal passageway 16 in a spaced-apart relationship with each other, and first and second discharge electrodes 46 and 48 extending through the first and second protection pipes 44 and 45 and protruding into the internal passageway 16.
The first and second protection pipes 44 and 45 are arranged one above the other in such a manner that they penetrate a through-hole 17 formed in the air conditioning case 10 and extend inwardly from a side wall 16a of the internal passageway 16. The first and second discharge electrodes 46 and 48 extend through the first and second protection pipes 44 and 45 and protrude into the internal passageway 16 at their tip ends. The first and second discharge electrodes 46 and 48 are designed to generate negative ions and positive ions by irradiating high voltage pulses into the air flowing through the internal passageway 16.
The negative ions and positive ions generated in the ionizer 40 are introduced into the evaporator 30 to sterilize bacteria and mold living in the evaporator 30 and also to deodorize the air supplied into the vehicle room, thereby enhancing the degree of cleanliness of the air introduced into the vehicle room and creating a comfortable vehicle room environment.
With the air conditioning system referred to above, however, moisture is condensed in and around the first and second discharge electrodes 46 and 48 of the ionizer 40 if the air introduced into the internal passageway 16 has high humidity. The condensed moisture is infiltrated into the first and second discharge electrodes 46 and 48, thus forming a water film which conducts an electric current between the first and second discharge electrodes 46 and 48. The electrical short through the water film causes a spark between the first and second discharge electrodes 46 and 48, consequently generating a discharge noise.